Composite diaphragm for diaphragm pumps

ABSTRACT

A composite diaphragm for diaphragm pumps comprises an elastomer body and a polytetrafluoroethylene (PFTE) coating on its back side. The elastomer body has a shape of a circular dish that has an edge region with a clamping area, a bottom and a flexible section of the diaphragm that connects the edge of the dish with the bottom. The flexible section of the diaphragm comprises a multitude of naps forming elevations on the elastomer backside of the elastomer body. The PFTE coating is a plane ring surface with the area of the flexible section of the diaphragm.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a composite diaphragm for diaphragmpumps that comprises an elastomer body and a coating ofpolytetrafluoroethylene (PTFE) on the product side. The elastomer bodyhas the shape of a circular dish that has an edge with a clamping area,a bottom, and a flexible section of the diaphragm that connects the edgeof the dish with the bottom.

[0003] The composite diaphragm is clamped in a diaphragm pump along theside of the edge, whereas the bottom of the composite diaphragm performslifting movements. The flexible section of the diaphragm is turnedinside out, with each lifting movement, whereby the roll-off movementsof the flexible material are observed in a radial section. In thetechnical field, the flexible section of the diaphragm is thereforereferred to also as a rolling loop.

[0004] 2. The Prior Art

[0005] When using composite diaphragms where the flexible section of thediaphragm without a profile has a uniform wall thickness, white stainingcan occur in radial lines in the PTFE-coating that indicates the onsetof material damage. As the damage to the PTFE-material progresses, thecomposite diaphragm loses its chemical resistance to aggressive conveyedmedia. The development of this damage limits the useful life of thediaphragm.

[0006] U.S. Pat. No. 5,349,896 discloses a design wherein the flexiblesection of the diaphragm is stiffened by radial ribs. The ribs extendfrom the transition area adjoining the bottom, up to the edge of thedish of the elastomer body. With a different number of radial stiffeningribs, it is possible to prevent the development of the damage describedabove. However, the roll-off property of the flexible section of thediaphragm deteriorates and the resistance to roll-off increases to aconsiderable extent.

[0007] When using this diaphragm with vacuum pumps, composite diaphragmsare preferred that have a smooth surface on the product side and restflatly against the surfaces of the pump when the latter is in operation.The invention provides a suitable composite diaphragm for diaphragmpumps that permits a long useful life without damage to the PTFE coatingand uses good roll-off properties when the pump is in operation.

SUMMARY OF THE INVENTION

[0008] The invention relates to a diaphragm having flexible section thathas a large number of naps forming elevations on the elastomer backsideof the elastomer body. In this design, the PTFE coating is formed in thearea of the flexible section of the diaphragm as a plane ring surface.The naps on the elastomer backside are preferably formed as cups with acircular or elliptic base area. The naps supply the flexible section ofthe diaphragm with punctual or periodic stiffening elements. The areasbetween the naps are flexible, so that the flexible section of thediaphragm can be turned inside out with little pressure. Thus, thesenaps prevent wear on the diaphragm because no folds caused bycompression or lines caused by buckling can form in the PTFE coating dueto these punctual stiffening elements. When in use, the compositediaphragm performs defined rolling movements, whereby the resistance toroll-off of the rolling loop is low.

[0009] Numerous possibilities are available for further variations ofthe composite diaphragm as defined by the invention. The naps arepreferably arranged lined up in at least two concentric circles,preferably with an angular division of between 5° and 30°. The naps thatare arranged in concentric circles may be arranged lined up in theradial direction in lines extending through the center of the circle.The invention also includes an embodiment in which the naps disposed inneighboring circles are disposed at offset angles in relation to eachother so that in the radial direction, one nap is disposed in front ofeach gap between two naps lined up in the peripheral direction.Furthermore, in at least one embodiment, the naps arranged in the circlewith the largest diameter and/or the smallest diameter are forming achain without gaps in the peripheral direction.

BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Other objects and features of the present invention will becomeapparent from the following detailed description considered inconnection with the accompanying drawings which disclose at least oneembodiment of the present invention. It should be understood, however,that the drawings are designed for the purpose of illustration only andnot as a definition of the limits of the invention.

[0011] In the drawings, wherein similar reference characters denotesimilar elements throughout the several views:

[0012]FIG. 1 is a section through one embodiment of a compositediaphragm as defined by the invention for diaphragm pumps.

[0013]FIG. 2 is a top view of the product side of the compositediaphragm shown in FIG. 1.

[0014]FIG. 3 is a view of the backside of the object shown in FIG. 1;and

[0015]FIGS. 4a to 4 h show further exemplified embodiments representedin each case by a view of the backside.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Referring to the drawings, FIG. 1 shows an example of a compositediaphragm for diaphragm pumps. The composite diaphragm is composed on anelastomer body 1 and a coating 2 of polytetrafluoroethylene (PFTE)applied to the product side. The elastomer body 1 is in the form of acircular dish comprising an edge 3 of the dish with a clamping area, abottom 4, and a flexible diaphragm section 5 connecting the edge of thedish with the bottom. A comparative view of the figures shows thatflexible section 5 of the diaphragm has a multitude of naps 6, whichform elevations on the elastomer backside of elastomer body 1. Inaddition, within the area of the flexible section of the diaphragm, thePTFE coating 2 is a plane ring surface.

[0017] Naps or protrusions can be formed as cups with a preferablycircular base area and are arranged in concentric circles in theexemplified embodiments with an angular division a of between 5° and30°.

[0018] In the exemplified embodiment shown in FIG. 3, naps 6 are linedup in the radial direction with a small spacing between each other inlines extending through the center of the circle. Furthermore, FIG. 3shows that naps 6 arranged on the circle with the largest diameter forma chain without gaps in the peripheral direction. Other arrangements ofnaps 6 are shown in FIGS. 4a to 4 h.

[0019]FIG. 1 shows that bottom 4 of elastomer body 1 contains a corethat is incorporated in the body by vulcanization, and comprises adevice for connecting a piston rod. This device can be in the form of areinforcing insert for receiving the piston rod or simply a gap formedon bottom Section 4. The design of this device can be in the form of asubstantially cylindrical gap. In the exemplified embodiment, theproduct side of the bottom has a convex shape. However, other shapes arenot excluded. The elastomer body 1 contains a textile reinforcementinsert 9 and, on its elastomer backside in the transition area betweenthe edge 3 of the dish and the flexible section 5 of the diaphragm,comprises a circular recess 10, as well as the ring-shaped grooves 11located in the transition area between the flexible diaphragm section 5and the bottom 4. The purpose of the recess 10 and the grooves 11 is toadditionally enhance the roll-off property of the flexible diaphragmsection 5.

[0020] The instruction as defined by the invention also covers compositediaphragms with bottoms not containing a metal core incorporated byvulcanization, but comprising a center opening for connecting it to apiston rod.

[0021] Accordingly, while at least one embodiment of the presentinvention has been shown and described, it is to be understood that manychanges and modifications may be made thereunto without departing fromthe spirit and scope of the invention as defined in the appended claims.

What is claimed is:
 1. A composite diaphragm for diaphragm pumpscomprising: a) an elastomer body shaped as a circular disk, the bodycomprising: i) a dish edge having a clamping area; ii) a bottom section;iii) a flexible diaphragm section connecting said dish edge with saidbottom section; iv) a plurality of naps forming elevations on anelastomer backside of said elastomer body; and b) apolytetraflouroethylene (PFTE) coating disposed on a product side ofsaid elastomer body, said coating being in a form of a plane ringsurface in an area of said flexible diaphragm section.
 2. The compositediaphragm as in claim 1, wherein said plurality of naps are shaped ascups.
 3. The composite diaphragm as in claim 1, wherein said naps arelined up in at least two concentric circles.
 4. The composite diaphragmas in claim 3, wherein said plurality of naps are arranged in concentriccircles with an angular division of between 5° and 30°.
 5. The compositediaphragm as in claim 4, wherein said plurality of naps are arranged inconcentric circles in a plurality of radially extending lines extendingthrough a center of said circular dish.
 6. The composite diaphragm as inclaim 4, wherein said plurality of naps are lined up in a radial mannerin offset angles in relation to each other so that at least one nap ofsaid plurality of naps is disposed adjacent to a gap between two napslined up in an adjacent peripheral concentric circle.
 7. The compositediaphragm as in claim 1, wherein said plurality of said naps arearranged to form a plurality of concentric circles comprising an innerconcentric circle having a smallest diameter and additional concentriccircles having larger diameters wherein said naps in said innerconcentric circle are alined to form a chain without gaps.
 8. Thecomposite diaphragm as in claim 1, wherein said plurality of said napsare arranged to form a plurality of concentric circles comprising anouter concentric circle having a largest diameter and additionalconcentric circles having smaller diameters wherein said naps in saidouter concentric circle are alined to form a chain without gaps.
 9. Thecomposite diaphragm as in claim 1, wherein said bottom section of saidelastomer body comprises: a) a core formed by vulcanization; and b) aconnector device disposed in said core for connecting a piston rod. 10.The composite diaphragm as in claim 1, wherein said bottom sectioncontains a center opening for connecting a piston rod.
 11. The compositediaphragm as in claim 1, wherein said elastomer body contains a textilereinforcing insert.
 12. The composite diaphragm as in claim 1, whereinsaid elastomer body has an elastomer backside and further comprises aplurality of ring shaped grooves on said elastomer backside in atransition area between said dish edge and said flexible section. 13.The composite diaphragm as in claim 1, wherein said elastomer body hasan elastomer backside and further comprises a plurality of ring shapedgrooves on said elastomer backside in a transition area between flexiblesection and said bottom section.
 14. The composite diaphragm as in claim1, wherein said elastomer body has an elastomer backside and furthercomprises a plurality of recesses on said elastomer backside in atransition area between said dish edge and said flexible section. 15.The composite diaphragm as in claim 1, wherein said elastomer body hasan elastomer backside and further comprises a plurality of recesses onsaid elastomer backside in a transition area between flexible sectionand said bottom section.